1. Field of the Invention
This invention relates to a semiconductor device and a method of manufacturing the same. More particularly, the present invention relates to a novel semiconductor device applicable to a surface emission light emitting device, an emission type display apparatus and an image sensor and also to a method of manufacturing such a semiconductor device.
2. Related Background Art
Conventionally, arrays of semiconductor devices such as diodes and transistors are prepared by regularly arranging semiconductor device chips that are manufactured individually and connecting them with wires. However, in the trend of downsizing and highly integrating electronic equipment in recent years, semiconductor devices are required to be arranged highly densely to form sophisticated single chips.
For example, the individual diodes of a photodiode array that is used for a light detecting section of a CCD chip mounted in an area image sensor minimally have a side as small as 3 μm. The design rule for the most advanced semiconductor processes that are used for CPUs operating as brains of personal computers and DRAMs, which are sophisticated memories, refers to 0.13 μm. This signifies that 0.13 μm is the lowest limit for structures that can be prepared on a commercial basis at present by means of semiconductor processing techniques using photolithography.
Known methods for preparing micro-structures include those for directly preparing micro-structures by means of a semiconductor processing technique such as a micro-pattern forming technique that typically utilizes photolithography using light with a shorter wavelength, electron beam exposure or X-ray exposure.
Meanwhile, apart from above-described semiconductor processing techniques, techniques of utilizing the phenomenon of self-organization of materials are also known. Such techniques are intended to realize novel micro-structures on the basis of a regular structure that is formed in the course of nature.
Research efforts are being paid for developing techniques of utilizing the phenomenon of self-organization because such techniques appear to be very promising for easily realizing micro-structures in the order of micrometers or nanometers.
As for anodization of aluminum, a porous oxide film coat (anodized alumina) is formed when an aluminum plate or an aluminum film formed on a substrate is anodized in an acidic electrolyte. (See R C. Furneaux, W. R. Rigby & A. P. Davidson, Nature, Vol. 337, P 147 (1989).) Such a porous oxide film coat is characterized by having a peculiar structure where very small cylindrical pores (nano-holes) of a diameter between tens to hundreds of several nanometers are arranged in parallel at intervals (cell size) of also tens to hundreds of several nanometers. When the gap separating the pores is tens of several nanometers or more, the pores show a high aspect ratio and their diameters are relatively highly uniform if viewed in cross section. The diameters and the intervals of the pores can be controlled to a certain extent by selecting the type of acid and regulating the voltage for anodization. Specifically, the intervals of the pores can be reduced by lowering a voltage. On the other hand, the thickness of the anodized film coat and the depth of the pores can be controlled to a certain extent by controlling the time for anodization.
Attempts are being made to apply anodization to various technical fields including coloring, magnetic recording mediums, EL light emitting elements, electro-chromic elements, optical elements, solar cells and gas sensors by using a technique of filling metal or semiconductor in the anodized nano-holes or a nano-hole replica technique. Furthermore, expectations are high for applying anodization to other technical fields including quantum effect devices such as quantum wires and MIM devices and molecule sensors using nano-holes as fields of chemical reactions (Masuda “Solid-state Physics” 31, 493 (1996)). Besides, Japanese Patent Application Laid-Open No. 2001-162600 proposes a light emitting device that is formed by burying ZnO in alumina nano-holes to show different intensities in the wavelengths of emitted light between in the direction parallel to and in the direction perpendicular to the substrate.
As an example of a process for forming micro-structures except for a process using nano-holes, Japanese Patent Application Laid-Open No. H10-321834 discloses a method of forming a wire-shaped agglomerate of metal micro-particles by utilizing the phenomenon that metal micro-particles are apt to be bonded together in a self-organizing manner due to their electric or magnetic interactions.
There is a report that single crystal nano-wires of p-type and n-type indium-phosphor are prepared by means of a vapor-liquid-solid (VLS) method of growing nano-wires in a self-organizing manner, using micro-particles of gold or the like as catalyst, and brought into contact with each other to cause them emit light (M. Lieber et al., Nature, Vol. 409, P 66 (2001)).
Now, as the demand increases for devices such as CCDs formed by incorporating semiconductor parts and made to be more downsized and sophisticated, semiconductor processing techniques such as lithography are required to show a precision level of 0.1 μm or higher. However, when deep ultraviolet rays or X-rays whose wavelength is even shorter are used for the light source, there arises a problem that preparation of a scaled down optical system is difficult and the light source inevitably has large dimensions. In the case of electron beam lithography, the drawing speed is low.
As pointed out above, difficulties dramatically increase to processes of directly preparing micro-structures as the size of individual elements diminishes by means of conventional semiconductor processing techniques including micro-pattern forming techniques such as photolithography.
Furthermore, processes of directly manufacturing micro-structures by means of semiconductor processing techniques are accompanied by additional problems including a poor yield and a high capital investment level. Therefore, there is a demand for techniques that can prepare micro-structures by a simple technique with an enhanced level of reproducibility.
It is, therefore, an object of the present invention to provide a semiconductor device of a size of the order of nanometers that can exhibit a quantum effect and an array of such semiconductor devices.
Another object of the present invention is to provide a method of manufacturing a high density semiconductor device and a device formed by using such an array.